Belowground Plot Experiment

NBC01 Konza Prairie Belowground Plot Experiment: Soil chemistry responses to experimental manipulations of fire, nutrients and mowing


To address the potential interactive effects of fire, aboveground biomass removal, and nutrient amendments on above- and belowground responses, a long-term field experiment was initiated in 1986 as part of the Konza Prairie Long-Term Ecological Research (LTER) program. The general goals of this experiment are: 1) to document both short- and long-term responses of plants and soils to fire, aboveground biomass removal (a surrogate for grazing in these small plots), and nutrient amendments (additions of N and/or P); and 2) to provide a better understanding of the mechanisms underlying tallgrass prairie responses to fire, aboveground biomass removal and nutrient enrichment. Effects of burning, mowing, and N + P additions on soil chemistry are measured on the 64 belowground plots at irregular intervals. Variables measured include P, NO3, NH4, Mn, Cu, K, Zn, Ca, Fe, Mg, Na, ph, Organic matter and Organic-N.

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To measure the effects of burning, mowing, and N and P fertilization on PH; available P; exchangeable, soluble and totl-N; cation exchange capacity; exchangeable Ca, Mg, and K; extractable Fe, Mn, Zn, and Cu; and total-P.


Location of Sampling Stations: Grid B-16 behind the stone house. The soil on the sites is an Irwin silty clay loam with approximately 15% slope. Sixty-four, 12 x 12 meter plots are arranged in a split-split design to measure burning, mowing, and fertilization effects.

Frequency of Sampling: Once per year, in the fall, every five years.

Variable Measured: Unless otherwise noted, the methods were used in measuring the variables listed below follow the procedures in 'Recommended Chemical Test Procedures for the North Central Region', Bulletin 499, North Dakota Agricultural Experiment Station, North Dakota State University, Fargo, North Dakota (1980) found in Appendix D.

  1. Nitrate and Exchangeable NR+ 4. A 10:1 mixture of 2 M KCl and soil are shaken for one hour and filtered. Nitrate and ammonium are measured using Technicon Autoanalyzer.
  2. Available P (Bray).
  3. Total-N (Kjeldahl).
  4. pH (1:1 water)
  5. Organic matter
  6. Exchangeable K, Ca, Mg; Cation Exchange Capacity. Five grams of soil are suspended in 50 mL of 1 M NH4OAc for 25 minutes, centrifuged, and filtered. This process is repeated three times. The suspension is washed with ethanol, centrifuged, and finally extracted with 2 M KCl. Exchangeable K, Ca, and Mg are determined in the original ammonium acetate washings, and CEC determined by measuring the residual NH4 in the KCl extract.
  7. DTPA-Extractable Cu, Zn, Mn, and Fe.

Methods: To avoid destructive over-sampling, all scientists on the Belowground Plots use the same samples. A composite of several 5 cm cores are taken from each plot, and sub-samples distributed to each investigator. A 50 g sub-sample is generally plenty for soil chemical analysis. Samples are air dried, ground to pass a 2 mm sieve, and stored in plastic containers for future analyses.

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